Name: modular protein complexes in cells
Uploaded: 2023-04-30T18:28:43.000Z
Duration: 1 min 57 s
Channel: JoVE

K12 Standards

Next Generation Science Standards

High School

Life Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

HS-LS1-1

protein-complexes-with-interchangeable-parts

Protein Complexes with Interchangeable Parts

Proteinkomplexe bestehen aus mehreren nicht-kovalent verknüpften Proteinen, wobei jede Komponente eine andere Funktion als der Komplex erfüllt. 
Eines oder mehrere dieser einzelnen Proteine können durch eng verwandte Varianten ersetzt werden, um einen alternativen Komplex zu erzeugen, der funktionell unterschiedlich ist.
Im Laufe der Evolution eines Organismus kann sich das Gen für ein nützliches Protein im Genom duplizieren. Diese duplizierte Kopie kann Mutationen durchlaufen, ohne die Funktion des ursprünglichen Proteins zu beeinträchtigen. 
Diese Mutationen erzeugen Familien verwandter Proteine. Dies ist eine der Möglichkeiten, wie eine Zelle einen Proteinkomplex erzeugen kann, der austauschbare Teile enthält. 
Die SCF-Ubiquitin-Ligase ist ein multimeres Protein, das aus fünf Untereinheiten besteht und dessen Funktion darin besteht, Ubiquitin-Moleküle an Zielproteine zu binden und sie für den Abbau durch proteolytische Enzyme zu markieren. 
Eine der Untereinheiten des Proteins, die F-Box, die für die Bindung an das Zielprotein verantwortlich ist, hat mehrere Varianten, die austauschbar sind. Eine Änderung dieser Untereinheit ermöglicht es dem Komplex, verschiedene Proteine für den Abbau zu markieren. 
Saccharomyces cerevisiae, allgemein bekannt als Backhefe, hat 11 Varianten von F-Box-Untereinheiten, die es der Ligase ermöglichen, Proteine zu markieren, die an einer Vielzahl von Zellprozessen beteiligt sind.
Zum Beispiel zielt das cdc4 F-Box-Protein auf Zellzyklusregulatoren wie Sic1 und Far1 ab, die Enzyme hemmen, die den Zellzyklus fördern. Ihr Abbau ermöglicht es, den Zellzyklus fortzusetzen. 
Die Variation der F-Box zwischen Organismen erzeugt Hunderte von unterschiedlichen Komplexen mit ähnlichen Funktionen, aber unterschiedlichen Zielen.

<ol>
	<li>Alberts et al., 6. Auflage; Seiten 159-160</li>
	<li>Kipreos, ET, & Pagano, M. (2000). Die F-Box-Proteinfamilie. Genombiologie, 1(5), REVIEWS3002. doi:10.1186/gb-2000-1-5-Bewertungen300</li>
</ol>

proteinkomplexe mit austauschbaren teilen

Gruppen von Proteinen können einen Komplex bilden, in dem jedes Protein in diesem Komplex eine andere Rolle bei der Ausführung der Gesamtfunktion des Komplexes hat. Oft können einige der Proteine im Komplex durch eine eng verwandte Variante ersetzt werden, um einen Komplex zu bilden, der viele der gleichen Komponenten enthält, jedoch funktional unterschiedlich ist.

Der SCF-Ubiquitin-Ligase-Komplex ist ein Proteinkomplex aus fünf einzelnen Proteinen. Dieser Komplex heftet Ubiquitin an andere Zielproteine, um sie zur Degradation zu markieren. Um diese Funktion auszuführen, ist eines der Proteine, das F-Box-Protein, dafür verantwortlich, an das Substrat zu binden, wodurch ein anderes Protein im Komplex, das Ubiquitin-konjugierende Enzym, Zugang zum Substrat erhält und Ubiquitin anhängen kann. Das F-Box-Protein hat mehrere austauschbare Varianten, sodass der Komplex verschiedene Substrate erkennen kann. Zudem können unterschiedliche Organismen verschiedene Sätze von F-Box-Proteinvarianten haben. Menschen haben 38 bekannte Varianten, Saccharomyces cerevisiae hat 11, Drosophila hat 22 und C. elegans hat 326. Diese Variation ermöglicht es dem Komplex, ein breites Spektrum an Proteinen zu adressieren, indem lediglich eine seiner Komponenten geändert wird.

Diese austauschbaren Varianten sind oft ein Ergebnis von Genverdopplung. Während der molekularen Evolution kann das Gen für ein nützliches Protein manchmal während der DNA-Replikation aus Gründen wie ektopischer Rekombination, Replikationsverschiebung, Aneuploidie, Polyploidie und Retrotransposition dupliziert werden. Diese duplizierte Kopie des Gens kann weitere Mutationen durchlaufen, während sie von einer Generation zur nächsten weitergegeben wird, da die Mutation die Funktion des ursprünglichen Gens nicht beeinflusst. Diese Mutationen führen zu Varianten eines Gens, die für Proteine wie das F-Box-Protein verantwortlich sind, die funktionell ähnlich sind, aber unterschiedliche Substratspezifitäten aufweisen.

Proteinkomplexe mit austauschbaren Teilen

Gruppen von Proteinen können einen Komplex bilden, wobei jedes Protein in diesem Komplex eine unterschiedliche Rolle bei der Gesamtausführung der Funktion des Komplexes spielt. ...

Education

Lehre

JoVE Core

Cell Biology

Zellbiologie

Unit 1

Einheit 1

Protein Function

Proteinfunktion

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

modular protein complexes in cells

Protein complexes in cells can be built from interchangeable parts. This modular design lets some complexes share common subunits while still changing their behavior.

A well-known example is the ubiquitin ligase complex called SCF. SCF stands for Skp1-Cullin-F-box, and it helps attach ubiquitin, a small protein tag, to target proteins. The core of SCF stays the same, but the F-box protein can change.

The interchangeable F-box subunit gives the complex its specificity. Different F-box proteins recognize different target proteins. This lets one core complex act on many different targets.

This kind of protein complex shows how cells use shared building blocks to create functional variety. By swapping one part, the same basic structure can take on new roles in protein control.

Modular Protein Complexes in Cells

ligand binding sites

Ligand Binding Sites in Proteins

Ligand binding sites are specific parts of a protein where a ligand can attach. A ligand is a molecule that binds to another molecule, often to help start or change a biological process. These sites matter because the shape and chemistry of the protein help determine which ligands can fit and bind. Proteins do not bind every ligand in the same way. The binding site provides a matching surface that supports a close interaction. In many cases, this interaction is important for how cells respond...

protein-protein interfaces

Protein Binding Surfaces and Contacts

Protein binding surfaces and contacts help proteins recognize and attach to each other. These interfaces are the regions where two proteins meet and interact. They are important for many cell processes and for how proteins work together. A protein-protein interface is not just a random touch point. It is shaped by the three-dimensional form of each protein. The matching surfaces allow a stable interaction to form when the proteins fit together well. Studying these interfaces helps explain how...

conserved binding sites

Conserved Binding Sites in Protein Families

Conserved binding sites are regions on proteins that stay similar across related proteins. These shared areas often help proteins interact with the same molecules. For this reason, they are useful clues when comparing protein families. A conserved site can help identify where a protein binds. It can also show which parts of the protein are important for function. When the same pattern appears in several proteins, it suggests that the site has been kept through evolution. Scientists look at...

cofactors and coenzymes

Enzyme Helpers: Metals and Vitamins

Enzyme helpers include cofactors and coenzymes. Enzymes are proteins made of amino acids, and the functional groups on those amino acids can drive many chemical reactions through ionic interactions or acid-base reactions. But amino acids alone cannot handle oxidation-reduction and group transfer reactions, so they need non-protein helpers called cofactors. Cofactors are often described as the chemical teeth of an enzyme. They can be metal ions or organic molecules called coenzymes. These...

cooperative allosteric transitions

Allosteric Changes in Protein Shape

Allosteric changes in protein shape help explain how some proteins switch between active and inactive states. These transitions are cooperative, which means a change in one part of the protein can affect other parts of the same molecule. The video focuses on how these shifts in shape support protein function. It also shows that allosteric transitions can be described with different models. In the concerted model, the protein changes shape as a whole. In the sequential model, the change happens...

protein kinases and phosphatases

Protein Kinases and Phosphatases in Cell Control

Protein kinases and phosphatases help control how proteins work in cells. Kinases add phosphate groups to proteins. Phosphatases remove those phosphate groups. This phosphorylation and dephosphorylation process can change a protein’s shape and activity. It is one way cells turn protein function on or off at the right time. These changes also help cells respond to signals and manage many cell activities. Together, protein kinases and phosphatases keep cellular signaling balanced. When one adds...

gtpases and their regulation

GTPase Molecular Switches and Control

GTPases are molecular switches that help control cell activity. They bind guanosine triphosphate, or GTP, and can change between active and inactive states. This switch-like behavior makes them important in many cell processes. The protein is active when GTP is bound and inactive when guanosine diphosphate, or GDP, is bound. GTPases can also turn themselves off by breaking down GTP into GDP. This built-in control helps cells regulate when the protein is on or off. Their activity is regulated...

covalently linked protein regulators

Protein Regulation by Covalent Bonds

Protein regulation by covalent bonds helps control how cells respond to changing conditions. A covalent bond is a strong chemical link, and in this context it can change how a protein behaves. Some regulators work by attaching a chemical group directly to a protein. This covalent change can alter the protein's activity, its location in the cell, or how long it stays active. Because the change is built into the protein itself, it can have a strong effect on cell function. Covalently linked...

protein complexes with interchangeable parts

Protein complexes in cells can be built from interchangeable parts. This modular design lets some complexes share common subunits while still changing their behavior. A well-known example is the ubiquitin ligase complex called SCF. SCF stands for Skp1-Cullin-F-box, and it helps attach ubiquitin, a small protein tag, to target proteins. The core of SCF stays the same, but the F-box protein can change. The interchangeable F-box subunit gives the complex its specificity. Different F-box proteins...

mechanical protein function

Proteins That Generate Cell Movement

Mechanical proteins help cells and tissues move. They turn chemical energy into force and motion. This process is important in many biological systems. These proteins are also called motor proteins. They interact with cell structures and can produce directed movement. In muscle cells, they support contraction. In other cells, they help with transport and shape changes. Mechanical protein function is a key part of how living systems work. It links protein activity to movement at the cellular...

structural protein function

Structural Proteins in Cells and Tissues

Structural proteins help cells and tissues keep their shape and strength. They are an important part of living systems because they provide support where it is needed most. Many structural proteins form fibers or other sturdy forms that resist stretching and wear. These proteins work as building materials in the body and help keep structures stable over time. Examples of structural proteins include collagen, actin, myosin, and keratin. Each one supports a different part of the body, but all...

protein networks

Mapping Protein Interaction Networks

Protein interaction networks show how proteins work together inside a cell. These networks help scientists see which proteins connect with each other and how those links support cell activity. Researchers often use online tools to build and study these networks. The transcript points to IntAct and STRING as examples of resources that can help predict and organize protein interactions. These tools make it easier to compare protein links and look for patterns in the network. Protein networks...

key terms and concepts

Explore how cells build protein complexes from interchangeable parts, including the SCF ubiquitin ligase and its F-box subunit that determines target specificity.

Modular Protein Complexes in Cells | JoVE K12

cell biology

JoVE Core Zellbiologie veranschaulicht komplexe zelluläre Prozesse in leicht verständlichen und dennoch umfassenden animierten Videolektionen. Diese Sammlung konzentriert sich auf die wesentlichen Bestandteile und Funktionen von Zellen, einschließlich Organellen und Membranen, Zelltransport und Zellenergie. Ergänzt wird sie durch Videos von Wissenschaftlern in Aktion, die die Anwendung der Zellbiologie in realen Forschungsexperimenten demonstrieren.

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

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Cell Structure

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Cytoplasm

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The Nucleus

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The Central Dogma

The DNA Helix

Nucleic Acids

DNA as a Genetic Template

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Chromosome Structure

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Protein Families

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Conservation of Protein Domains

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Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Globular and Fibrous Proteins

Translation

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Intrinsically Disordered Proteins

Ribosomes

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Protein Complex Assembly

Protein and Protein Structures

Conjugated Proteins

Proteins: From Genes to Degradation

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Proteins are polymers of amino acids linked together by peptide bonds. Proteins and polypeptides are interchangeably used to refer to long chains of amino ...

Ligand Binding Sites

Protein Organization

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Protein-Protein Interfaces

Protein Folding

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Conserved Binding Sites

Cofactors and Coenzymes

Enzymes are proteins made of amino acids. The functional group of each constituent amino acid catalyzes a wide variety of chemical reactions via ionic ...

Cooperative Allosteric Transitions

Protein Kinases and Phosphatases

GTPases and their Regulation

Covalently Linked Protein Regulators

Mechanical Protein Function

Structural Protein Function

Protein Networks

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells. [Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.]

Levels of Organization

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Animal and Plant Cell Structure

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structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

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Overview of Human Digestion

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Accessory Organs

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Lipid Digestion

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Protein Digestion

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Carbohydrate Digestion

Carbohydrate digestion and metabolism break down simple and complex carbohydrates from food into saccharides (i.e., sugars) for the body to use as energy. ...

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Overview

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The Parasympathetic Nervous System

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The Sympathetic Nervous System

Overview

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Oogenesis

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What is a Sensory System?

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Fertilization

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an-introduction-to-the-zebrafish-danio-rerio

An Introduction to the Zebrafish: Danio rerio

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Physiology of the Circulatory System

Homeostasis
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Anatomy of the Circulatory System

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Anatomy of the Heart

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Measuring Circulatory System Function in Humans
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Blood Flow

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Blood Withdrawal I

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Kidney Structure

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Blood Withdrawal II

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN
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Overview

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Bone Remodeling

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Spermatogenesis

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Bone Structure

Within the skeletal system, the structure of a bone, or osseous tissue, can be exemplified in a long bone, like the femur, where there are two types of ...

Breathing

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. [Clarification Statement: Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, and organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.] [Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.]

HS-LS1-2

What is Homeostasis?

Maintaining homeostasis requires that the body continuously maintain its internal conditions. Each physiological condition has a particular set point, ...

Negative and Positive Feedback

Homeostatic Imbalance

Homeostasis is the maintenance of a stable internal environment within the body, which is crucial for the proper functioning of cells, tissues, organs, ...

Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis. [Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.] [Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

HS-LS1-3

Modular Protein Complexes in Cells

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